The parent application is hereby incorporated by reference in its entirety and is directed to a method and system for the in situ removal of radionuclides from a groundwater radionuclide contaminated water source, such as a moving, underground water plume. The parent application provides for a trench or a bed above groundwater level and containing therein, granulated zeolite material, and with the trench having a bottom water barrier lining.
Groundwater containing the radionuclides is distributed, such as by pumping from a water source, generally uniformly, over the top of the zeolite material in the trench, in order to filter the radionuclide contaminated water source through the zeolite bed to remove the radionuclides, or rather metal contaminants, cations, i.e., using the zeolite material, such as by ion exchange with the zeolite material, or more typically by capture of the radionuclides or other contaminates in the internal lattice structure of the zeolite material. The system and method also provides for the discharge of the treated water from the bottom of the trench containing the zeolite material, or recycling all or part of the treated water, as desired, back to the trench for continuous treatment, until the desired level of treatment water is obtained. The system and method also includes for the in situ closure of the trench with the zeolite material, by covering the trench of the zeolite material, for example, with a plastic or clay layer, and subsequently burying the trench with soil to close the bed after the exhaustion of the process by the zeolite material, thereby providing for the in situ treatment and removal of radionuclides or other contaminants from the contaminated water source.
Septic systems are commonly used for the treatment of domestic wastewater, and such septic systems include a septic tank to receive a flowing wastewater effluent or sewerage, typically, from a residence or small business, and which effluent sewerage includes solid matter, and wherein the septic tank bacteria breaks down the sewerage and solid matter. The septic system normally includes one or more leaching fields to receive the continuously flowing treated effluent or xe2x80x9cgrey waterxe2x80x9d from the septic tank. Generally, the septic systems are employed in those suburban or farm areas where there is a lack of a central or municipal sewerage facility. Approximately ⅓ of all households in the United States dispose of domestic wastewater through the use of septic tank systems. However, due to poor construction and maintenance or geologic conditions, septic tank systems have polluted underlying ground waters and surface waters, such as streams, rivers, ponds, estuaries and bays.
While septic systems with the septic tank and leach field are acceptable, septic system problems are magnified by the fact that in many areas, particularly rural communities, a substantial reliance on subsurface sewage disposal systems is paralleled by a reliance on private wells for drinking water supplies. These problems, which stem from the nutrient-rich composition of the septic tank effluent water when it reaches the leach field, create hazardous conditions in certain areas. For example, where soils are sandy and well-drained, and on-site groundwater is also a source of drinking water for the domicile, nutrient-rich water from leachate can contaminate the drinking water source. Nutrient-rich leachate from home septic systems can cause unacceptably high nitrate levels in drinking water, resulting in xe2x80x9cblue babyxe2x80x9d syndrome and other health problems. Nitrogen is a key nutrient of concern, because it contributes to the eutrophication of surface water, as well as posing health hazards in groundwater. Nitrates in drinking water, derived from wells where septic system are also present on-site, constitute a widespread, intractable problem throughout the United States. It is therefore desirable to provide for a new and improved septic system and method for the treatment of wastewater effluent and sewerage.
The invention relates to a zeolite-augmented bed septic system and method for the treatment of wastewater, particularly through the use of zeolite material in an adjunct tank between the septic tank and the leaching field.
In particular, the invention concerns a zeolite bed septic system and method which includes a filter media bed between the septic tank and the zeolite bed; and optionally, an ion sensor monitoring system and method for ammonium ions and a regeneration system.
The invention relates to a septic system for the removal of contaminants, particularly nitrogen contaminants, such as ammonia from wastewater effluent, which septic system comprises a source of wastewater containing nitrogen and other contaminants, such as ammonia and phosphorus, and typically a residence or small business employing such a septic system, and more particularly, wherein the septic system is located in a very low-soil absorbing geographical area, such as Cape Cod. The system includes a septic tank connected to said wastewater source to receive septage, including solid matter, and the septic tank containing bacteria therein for the treatment of said septage and to provide a wastewater treated effluent from said septic tank. The system also includes a zeolite-filled tank (or bed) in the ground, above groundwater, to receive the wastewater effluent from the septic tank and one or more leaching fields. The second tank contains granulated zeolite material selected to capture and retain the nitrogen and other nutrients and contaminants in the wastewater effluent from the septic tank. Inflow to the zeolite tank is composed of nutrient-rich wastewater effluent from the septic tank. Outflow from the tank is effluent that has been filtered by the zeolite in the tank and no longer contains nutrient contaminants. Outflow from the tank is piped to a standard leach field where it will leach into the groundwater. A septic system also includes a means to regenerate periodically, as desired, the zeolite material in the zeolite tank when the zeolite material can no longer substantially capture the nitrogen contaminants from the treated wastewater effluent, and includes a means to remove the displaced nitrogen contaminants generated from the regeneration of the zeolite material.
Generally, the septic tank and the zeolite tank are employed as an underground septic system, above groundwater level, in a well-drained, typically sandy soil, and wherein the nitrogen contaminant in the wastewater effluent comprises primarily nitrates and ammonia, and wherein the zeolite material comprises a granulated, natural zeolite material, placed in one or more concrete tanks, preceding the leach field trench or bed. The zeolite material in the tank may be regenerated in a number of ways; for example, by the use of liquid solution with cations or other compounds to displace the nitrogen contaminants, such as ammonia, captured within the zeolite material; the means are provided to remove the released nitrogen contaminants, such as by the employment of a pump means to pump out the septic tank or leaching field, or a heating means to heat the zeolite material to displace the nitrogen contaminants, such as ammonia, as a gas and either to permit the escape of the gas or to capture the gas. The zeolite material in the zeolite tank field may also be regenerated by nitrifying bacteria introduced into the zeolite material, which may be included as nonpathogenic organisms within the zeolite material.
The zeolite tank may be equipped with shut-off valves at the intake and outflow, and piped openings on top of the tank, through which a flushing hose may be introduced to flush the zeolite with regenerating fluid, which is then extracted. The extracted regenerating fluid then contains the nitrogen contaminants previously stored in the zeolites, and the zeolites are recharged and ready to receive and decontaminate effluent from the septic tank.
The invention also comprises a method for the removal of nitrogen contaminants, more particularly ammonia, from wastewater effluent from a septic system, and which method would comprise introducing a wastewater effluent from a septic system and containing nitrogen contaminants, such as ammonia, into one or more zeolite-filled tanks, and which one of the zeolite tanks would comprise regenerable particulate zeolite material selected to capture, and retain therein the nitrogen contaminants in the wastewater effluent from the septic system. The method would include periodically regenerating the zeolite material after the zeolite material has been substantially exhausted, by capturing the nitrogen contaminants, by treating the zeolite material, such as by, but not limited to heating liquid solutions, flushing with saline water, bacteria, or other means to otherwise remove or displace the captured nitrogen contaminants from the zeolite material in the zeolite tank, to restore the zeolite material in the zeolite tank for reuse. The method would include removing the displaced nitrogen contaminant material by separately treating the escaped contaminant material, or permitting the material to be discharged into the atmosphere, or otherwise treating or removing the displaced nitrogen material from the zeolite tank contained in the septic system.
One embodiment of the zeolite septic system and method may be called the Cape Cod disposal system. This embodiment consists of an underground tank filled with zeolite material, installed at a residence or small business as an adjunct to a septic tank, to be an adjunct to the typical septic tanks and leach field commonly used in a home septic system. The zeolite material in the tank removes ammonia and other contaminants received from the septic tank wastewater. Ammonia in wastewater is a major problem on Cape Cod, and similar soil areas (e.g., Long Island, N.Y.) that generally resisted installing municipal sewers in favor of individual septic systems. The septic systems (mainly the leach fields) cause nitrogen loading in the rivers, ponds, groundwater, and coastal areas, leading to algal blooms and eutrophication of water bodies. One way to remedy the situation would be to construct wastewater treatment plants, connect homes to public sewer, treat the waste in the treatment plant and pump the effluent out to the ocean. The Cape Cod disposal system is a much less expensive way to remedy the problem, and does not contribute to, and in fact prevents, ocean eutrophication.
An ordinary leach field or soil absorption system is constructed in coarse-grained sandy soil of varying mineral composition. Water must be able to percolate through the soil quickly in order for a site to be approved by regulating agencies for leach field construction. Wastewater enters a leach field by way of a distribution box and piping from the septic tank. The immediate source of the wastewater is a septic tank, into which all of the bath, kitchen, and laundry wastes from a home are piped. The solids settle to the bottom of the septic tank, and the liquid wastewater effluent flows out of the tank and into the leach field through a pipe exiting near the top of the tank. The wastewater is distributed by a distribution box and gallery piping along the top of the one or more leaching beds.
Rather than the discharge of the treated wastewater effluent derived from a septic tank or cesspool into a leach field, it is recognized that said effluent may be discharged in a receptor tank or tank trench for removal or other treatment prior to discharge into the soil or discharged at a remote location or treatment facility, rather than to a leach field.
Regulations and construction restrictions are imposed by governmental agencies to assure that the leach field will function properly. The soil must be well drained. Bedrock and stony areas are prohibited as building sites, as are steep slopes and unstable areas. Disturbed ground may not be used, nor may low lying areas near coastal areas or surface waters. Leach fields are always constructed in the unsaturated zone, well above groundwater, and as far as possible from wells and water supplies.
Geologically, Cape Cod is a glacial outwash plain composed of clean quartz sands (the sands have actually been very well washed by the glacial meltwater). The groundwater under the sands is a sole source aquifer, which has been granted special protection status, because it is the only source of fresh water on Cape Cod. All of the surface water bodies on the Cape are directly connected to this aquifer. Cape Cod is a nitrogen-sensitive area. One cause of nitrogen sensitivity on Cape Cod is the difference in soil mineralogy between Cape Cod, with its stable quartz sands, and continental areas which contain soils of varying compositions, charges, and grain sizes. Clays are typical constituents of continental soils, and clays generally have good absorptive properties. Cations, like nitrogen, are attracted to the charged region between the clay layers and are held between the layers by ionic bonds. Other types of silicate minerals typical of continental areas have varying absorptive properties, depending on their crystal structure, ionic charge, and composition.
On the opposite end of the soil spectrum are Cape Cod sands, which are non-absorptive, mono-mineralic quartz grains with a framework crystal structure that has no charge, and no spaces in the framework where cations can enter. On Cape Cod, there is nowhere for the nitrogen from the leach fields to go, but into the aquifer and surface waters, because the quartz sands will not absorb it. This in turn creates algal blooms, weed-choked ponds and low oxygen conditions in the water, unfavorable for fish and shellfish. Percolation (xe2x80x9cpercxe2x80x9d) tests are required prior to leach field construction to ensure that the soil will drain well enough for a septic system to function. On Cape Cod, the soils are too well-drained for an ordinary septic system to function properly, allowing contaminated water to leach into the aquifer.
The Cape Cod septic zeolite waste disposal system and method, when used with an ordinary, functional septic tank, will remove nitrogen and other unwanted constituents from wastewater, and hold them within the tank until they are removed by reactivation of the zeolite. Reactivation of the zeolite material in the zeolite tank would be part of the normal maintenance of the septic system. The size of the zeolite tank could be adjusted to allow for reactivation of the zeolite tank to coincide with septic tank pumping.
The size of the Cape Cod leach field may be calculated, for example, on a xe2x80x9cgallons per dayxe2x80x9d basis. A two bedroom home is required by state regulations in Massachusetts to provide a septic system able to handle 220 gallons of wastewater per day, while a 10 bedroom bed-and-breakfast must handle a minimum of 1000 gallons per day. A generous estimate for the amount of granulated, natural, zeolite material required for a zeolite tank for the bed-and-breakfast would be xc2xd ton, which would occupy 15 cubic feet of space. The cost of crushed and screened clinoptilolite, one example of a zeolite capable of removing 99% of nitrogen from septic waste material effluent, is reported to be between $200 to $300 a ton.
Zeolites have been used as a treatment for wastewater in municipal wastewater treatment plants and combined sewer overflows in some U.S. cities and Japan. Clinoptilolite has been the zeolite of choice, but experiments show that phillipsite, mordenite and erionite also work well. Natural zeolites are much less expensive than synthetic zeolites, though synthetic zeolites would also work well in the Cape Cod disposal system. In a demonstration project of an exchange-filtration system for wastewater treatment using natural clinoptilolite, conducted by the EPA in Syracuse, N.Y., ammonia in wastewater effluent was reduced to 0.02 mg/l. Significant reductions in bacteria, oxygen-demanding constituents, and other pollutants were realized as well.
Breakthrough exchange capacity occurs when the zeolite material can no longer absorb ammonia. Each type of zeolite has an associated exchange capacity, which determines when the Cape Cod disposal system requires regeneration. Once regenerated, the zeolite tank will continue to remove pollutants from wastewater. Several means of regeneration are available, including chemical, thermal and biological. Chemical methods employ a liquid solution containing a cation that enters the zeolite molecule, displacing the ammonia, which is then carried off in solution and may be used as fertilizer. Calcium and sodium are suitable cations. A simple regenerating liquid is sodium chloride (NaCl) in the same concentration as seawater.
Thermal regeneration is also very effective for complete regeneration of the zeolite material. Heating coils in the zeolite tank that could heat the spent zeolite up to 500 degrees celsius would produce a system that could be regenerated by a switch that controls the heating coils. A gas trap could be used to capture the nitrogen that off gases.
Biological regeneration by nitrifying bacteria would occur over time if the tank were aerated. Static ammonia exchange tests indicate that clinoptilolite will regenerate 80% of its ability to remove ammonia in 30 to 40 days, using only the naturally occurring nitrifiers. When the system is spiked with additional nitrifying bacteria, the regeneration time is halved. Since regular maintenance of septic systems is required by state law, regeneration of the zeolites in the Cape Cod waste disposal system should be performed by technicians coincident with tank pumping to ensure compliance and proper function.
In a further embodiment, the zeolite septic system and method include a media bed and/or secondary treatment tank to treat the wastewater effluent from the septic tank, to reduce suspended solids and biological oxygen demand (BOD) for the wastewater effluent treated in the septic tank or bed. The media bed comprises filter material, typically, randomly-dispersed, particulate material of porcelain; plastic; foam; or other inert filter material to lower the suspended solids in the wastewater effluent to a selected lower suspended solid particle concentration, for example, less than an average of about 50 ppm, i.e., less than about 15 to 20 ppm, and typically, to an average particle size of less than about 10 microns. The reduction of suspended solids and bacteria in the wastewater effluent to the zeolite tank reduces the tendency of the zeolite tank to clog in use.
Therefore, in one.embodiment, the media bed and secondary treatment tank comprise a pump chamber that connects the septic tank and the zeolite tank, which pump chamber would precede the zeolite tank. The pump chamber contains inlet and outlet pipes; a dosing pump; and a media bed or tank above the pump chamber that contains filter media, such as STYROFOAM(copyright) or pieces of plastic over which the septic tank effluent is pumped and filtered. Preferably, the pump chamber is oxygenated by means of a fan open to the outside. Septic tank wastewater effluent passes through the inlet pipe into the lower part of the pump chamber. When the water reaches the height of the pump, it is pumped over the media in the top of the pump chamber. After it has trickled through the media, it flows into the outlet pipe and into the zeolite bed, in a clarified state, with lower suspended solids and biological oxygen demand (BOD), thereby helping to prevent clogging in the zeolite tank. Optionally, the tank containing the pump chamber has an alarm that alerts the user if the pump fails to turn on at the appropriate time, while an optional second pump may be employed to insure the system works continuously.
Also, it has been discovered that an advantage may be gained by placing the outlet pipe of the zeolite tank at the base of the tank, rather than level with the inlet pipe. The clarified septic tank effluent from the pump chamber would then come into closer contact with the zeolite material and would not tend to remain in pore spaces between the zeolite grains. In this embodiment, the septic system effluent may be distributed over the zeolite in the tank through a distribution system that might spray the effluent evenly over the zeolite grains or allow it to trickle evenly through the bed of zeolite. Vents or air spaces above and below the zeolite tank allow the ion exchange process to occur in an oxygenated environment.
The zeolite bed may be composed of multiple layers of different zeolite material or particle size. For example, the lowermost layer of zeolite in the bed may contain approximately 70 to 75 percent of the total volume and of about 20xc3x9750 mesh or lower in grain size. The top layer of zeolite may contain 25 to 30 percent of the total volume of zeolite and is composed of a coarser grain size, for example, about 14xc3x9716 mesh or higher. The difference in zeolite particle or grain size allows the septic tank effluent to pond slightly over the finer grained zeolite material.
Optionally, the zeolite septic system and method may include an ion or other sensor system to monitor the ammonium content of the decontaminated water from the zeolite tank or the ammonia saturation of the zeolite material, so that automatic or manual regeneration of the zeolite material or other action taken will maintain the efficiency of nitrogen contaminant removal. The monitor and control system comprises an ion sensor to monitor and measure, generally by electrical conductivity, the saturated ammonium ion or ammonia concentration and suitable valves, pipes, and pumps.
In another embodiment, the system includes a source of backflush fluid, typically saltwater, with associated piping and pump to backwash periodically the zeolite bed, when the ion sensor detects that the zeolite bed requires regeneration, or at periodic time internals, where no ion sensor is necessary. The system may provide automatic backwashing at selected, detected ion sensor levels, generally, with the backwash water directed back into the backwater source tank.
An ion sensor is placed into the zeolite tank to recognize the state of ammonia saturation in the zeolite, and generally, the ion sensor would be placed near the outlet pipe. When the ammonium ion in the effluent reaches a selected concentration, for example, a concentration of 5 to 10 ppm or in regeneration, an alarm would alert the user that system maintenance, by backwashing the zeolite, is required. The ion sensor may also automatically trigger a backwash cycle to begin. In this embodiment, an additional tank of saltwater, or other ionic or regeneration material situated next to the zeolite tank, flushes the zeolite tank to carry out the ion exchange or regeneration process. Valves on the inlet and outlet pipes automatically direct the flow from the backwash tank to the zeolite tank. The ion sensor detects when backwashing is complete, which automatically ends the backwash cycle, and directs the backwash water into the backwash tank.
The invention will be described for the purpose of illustration only in connection with certain illustrated embodiments; however, it is recognized that various changes, modifications, additions and improvements may be made by those persons skilled in the art to the septic system, zeolite tank, and leach field method and system of the invention, as described and disclosed, without departing from the scope of the invention.